Surface modification of gold and quantum dot nanoparticles with chitosan for bioapplications.

Gold (Au) and quantum dot (QD) nanoparticles, which have been extensively used in many fields, were encapsulated with a natural polymer, chitosan, to improve their biocompatibility. Characterization was performed using ultraviolet-visible, dynamic light scattering, atomic force microscopy, and transmission electron microscope analyses. It was found that a Au/chitosan ratio of 1:1 and smaller produced chitosan-encapsulated Au nanoparticles of a sufficiently small size, and this result was then applied in the chitosan encapsulation of QDs. The biocompatibility of both types of nanoparticles was assessed in cell culture studies using HT29 human colon carcinoma and NIH 3T3 mouse fibroblast cells. MTT and trypan blue exclusion assays revealed that both chitosan-encapsulated Au nanoparticles and QDs exhibited improved biocompatibility over their bare, nonencapsulated counterparts. Therefore, this study showed that chitosan could be used to encapsulate both Au nanoparticles and QDs in order to enhance their biocompatibility. The approaches developed in this study can also be extended to other nanoparticles for bioapplications as well.